This is a collaborative project between Oregon hospitals, infection control staff, Oregon Public Health Division's Emerging Infections Program (EIP) and the Centers for Disease Control and Prevention (CDC).

The project began because of an unusually early start to the 2003-2004 influenza season coupled with reports of influenza-associated complications and deaths in children. As a result, EIP states began conducting population-based surveillance to assess the burden of influenza in pediatric patients. Adult influenza hospitalization surveillance was added in 2005.

The primary objective for these surveillance projects is to determine the rate of influenza among these populations as well as describe the characteristics of children and adults with severe flu. These projects also contribute to evaluations of current influenza vaccine recommendations.

Case definitions

Enhanced surveillance is conducted for all ages hospitalized with lab-confirmed influenza (including rapid tests) for residents living in Washington, Clackamas, and Multnomah counties.